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A model for characterizing the influence of noncoaxial stress and field on hysteretic magnetic properties was presented. It was shown that at an angle of 0 degrees, coercivity tends to decrease in the transition from negative to positive stress. At 90 degrees, the opposite behavior was observed when coercivity increased as positive stress changed to negative.

A study was conducted to analyze fatigue damage in materials using magnetic measurement methods. Fe-C alloy bars were austenitized at 905 degrees C for two hours. The samples supported a ferrite/pearlite structure and were machined to an hour glass shape. Experimental results indicated that the hysteresis characteristics of the samples cycled at various strain amplitudes varied systematically with expended fatigue life.

A study of the effect of non-magnetic particles on the magnetic properties of nickel is reported. The presence of inclusions is known to affect the structure sensitive magnetic properties of materials. In this work, two kinds of inclusions, namely, alumina particles and voids were studied and their effects on the magnetic properties were investigated. Powder metallurgy techniques were used to produce nickel compacts with varying amounts of alumina present. While coercivity increased with the volume of inclusions present, initial permeability decreased. Other properties such as remanence and hysteresis loss did not show a significant variation due to their sensitivity to the demagnetizing effects of the inclusions. An attempt has been made in this paper to explain quantitatively the variation in the magnetic properties in terms of the amount of inclusions present. Magnetic property measurements could be a useful non-destructive technique for determining porosity in magnetic materials.

Results of inspection creep damage by magnetic hysteresis measurements on Cr-Mo steel are presented. It is shown that structure sensitive parameters such as coercivity, remanence and hysteresis loss are sensitive to the creep damage. Previous metallographic studies have shown that creep changes the microstructure of the material by introducing voids, dislocations, and grain boundary cavities. As cavities develop, dislocations and voids move out to the grain boundaries; therefore the total pinning sources for domain wall motion are reduced. This, together with the introduction of a demagnetization field due to the cavities, results in the decrease of both coercivity and remanence. Numerical computations with a modified Jiles-Atherton model are presented which are consistent with the proposed mechanisms.

The use of Barkhausen signal analysis for evaluating fatigue damage in steel structural components was investigated. The results showed that Barkhausen effect measurements can be effective in accurately predicting impending fatigue failure. It was shown that changes in magnetic properties were sensitive to microstructural changes occuring at the surface of the material throughout the fatigue life.